Introduction to Basic Manufacturing Processes and ... - always yours

398 Introduction to Basic Manufacturing Processes and Workshop Technology
The machine tools involve various kinds of machines tools commonly named as lathe,
shaper, planer, slotter, drilling, milling and grinding machines etc. The machining jobs are
mainly of two types namely cylindrical and flats or prismatic. Cylindrical jobs are generally
machined using lathe, milling, drilling and cylindrical grinding whereas prismatic jobs are
machined using shaper, planner, milling, drilling and surface grinding.
In metal cutting operation, the position of cutting edge of the cutting tool is important
based on which the cutting operation is classified as orthogonal cutting and oblique cutting.
Orthogonal cutting (Fig. 20.2) is also known as two dimensional metal cutting in which the
cutting edge is normal to the work piece. In orthogonal cutting no force exists in direction
perpendicular to relative motion between tool and work piece. Oblique cutting (Fig. 20.3)
is the common type of three dimensional cutting used in various metal cutting operations
in which the cutting action is inclined with the job by a certain angle called the inclination
angle.
Feed
Tool
Feed
Cutting tool
Orthognal cutting
Fig. 20.2 Orthogonal cutting
Oblique cutting
Fig. 20.3 Oblique cutting
20.2 CUTTING TOOL
Cutting tools performs the main machining operation. They comprise of single point
cutting tool or multipoint cutting tools. It is a body having teeth or cutting edges on it. A
single point cutting tool (such as a lathe, shaper and planner and boring tool) has only one
cutting edge, whereas a multi-point cutting tool (such as milling cutter, milling cutter, drill,
reamer and broach) has a number of teeth or cutting edges on its periphery.
20.2.1 Single Point Cutting Tools
There are mainly two types of single point tools namely the solid type as shown in
Fig.20.4 and the tipped tool (Fig.20.5). The solid type single point tool may be made from high
speed steel, from a cast alloy. Brazed tools (Fig.20.6) are generally known as tool bits and are
used in tool holders. The tipped type of tool is made from a good shank steel on which is
mounted a tip of cutting tool material. Tip may be made of high speed steel or cemented
carbide. In addition to this, there are long index-able insert tools and throwaway. The Insert
type tool throwaway refers to the cutting tool insert which is mechanically held in the tool
holder. The inserts are purchased which are ready for use. When all cutting edges are used,
the insert is discarded and not re-sharpened. These tools can be further classified depending
upon the operations for which they are used and the type of the shank (straight or bent shank
type). Tools may be of the types planning tools, turning tools, facing tool, boring tools, parting
and slotting tools etc.
Different types of carbide tips are generally used on tipped tool. In general the straight
shank type tools are cheaper to manufacture as compared to bent shank type. But bent shank
type can be used for turning either longitudinal or cross feed without resetting and for